reworked com stack.

- prepared for use of CRC8
- organized code in more files
- recv stats message now contains crc errors and io errors

avr/com_twi.asm

@@ -0,0 +1,56 @@
+
+; ***************************************************************************
+; code
+
+.cseg
+
+
+; ---------------------------------------------------------------------------
+; Enqueue a TWI Bus Member packet.
+;
+; IN:
+; - R16: destination address
+; - R1 : Address of the bus member
+; - R2 : availability (0=not available, 1=available)
+; OUT:
+; - CFLAG: set if okay, clear otherwise
+; MODIFIED REGS: R16, R17, R20, X (R15, Y)
+
+CPRO_EnqueueTwiBusMember:
+  push r16
+    rcall COM_AllocBufferAndGetXY ; (r16, r17, r21)
+  pop r16
+  brcc CPRO_EnqueueTwiBusMember_error
+  clr r17                         ; r17: XOR byte
+  ; write header (dest address, msg length)
+  st X+, r16                      ; destination address
+  eor r17, r16
+  ldi r16, 4                      ; 4 bytes payload
+  st X+, r16
+  eor r17, r16
+  ; write payload
+  ldi r16, CPRO_CMD_TWIBUSMEMBER   ; send command
+  st X+, r16
+  eor r17, r16
+  lds r16, comAddress             ; send source address
+  st X+, r16
+  eor r17, r16
+  mov r16, r1                     ; send i2c bus member address
+  st X+, r16
+  eor r17, r16
+  mov r16, r2                     ; send i2c bus member availability
+  st X+, r16
+  eor r17, r16
+  ; store XOR byte
+  st X+, r17
+  ; mark buffer as enqueued with PRIO "info" (limited amount of retries)
+  ldi r20, COM_BUFFER_PRIO_INFO
+  rcall COM_EnqueuePacket      ; (R15, R16)
+  brcc CPRO_EnqueueTwiBusMember_error
+  sec
+  ret
+CPRO_EnqueueTwiBusMember_error:
+  clc
+  ret
+
+